Failing to Connect to the VU by Dialing the VU Access Code in the Local Regeneration Network

An outer-office PSTN user dials the VU access code XXXX4000. The PSTN network sends 4000 to the local regeneration node, the local regeneration node sends 4000 to the central node for VU access, and the VU plays announcements. An intra-office user dials the access code 4000 and the VU plays announcement. The preceding are the normal procedures for the outer-office and intra-office users to access the VU.

Fault description:
An outer-office user dials the VU access code, but fails to access the VU and hears no announcements. An intra-office user dials the VU access code and hears the announcements played by the VU.

Handling Process

Step 1 Run the show tkc command to check the trunk status. The trunk works correctly.

Step 2 Dial another number as an outer-office user and dial a PSTN number as an intra-office user. Both calls are successfully connected, which indicates that the trunk works correctly.

Step 3 Check the prefix 4000 on the local gateway. The prefix 4000 does not exist. Add the prefix 4000 and find that the VU works correctly. The possible cause is that the prefix 4000 was deleted.

Step 4 Check error logs and locate the records about deleting the prefix 4000. This verifies the assumption in the previous step.

As the VU still works correctly for intra-office users, the most possible cause is that the trunk is faulty.

Suggestions

When a call is connected to the local gateway in the local regeneration network, the local gateway first analyzes the call prefix. If an intra-office or VU prefix is detected, the local gateway connects the call to the central gateway. If an outer-office prefix is detected, the local gateway connects the call to the outer-office user. If none of the intra-office, outer-office, and VU prefixes is detected, the local gateway returns a failure message.